Abstract : In-Situ measurements of the speed of sound in the upper ocean have revealed the existence of significant dispersion and large fluctuations over the frequency range 25-80 kHz. The near-surface values of c ranged from +6 M/sec to -3 M/sec relative to the bubble-free value, with a maximum estimated error of 0.5 M/sec. It was possible to identify bubbles of 'surface' radius centered around 54 microns down to 4.3 meter depth as well as a population centered around 124 microns (at 4.3 M) found at all depths. The speed fluctuation showed near-Faussian probability density functions except at the dispersion center frequencies. The standard deviation of the speed varied from 0.27 M/sec for 58.0 kHz to 0.52 M/sec at 69.6 kHz. (Author)